The present invention relates to an identity card and to a method of producing such an identity card.
Identity cards of the type in question here are, for example, check cards, credit cards, membership cards and the like, the card structure corresponding generally to ISO Standard 7813 (DIN 9781).
Such identity cards are designed for example as multilayer plastic cards. On the front of the card there is general information, such as the name of a credit institute, and user-related information, such as the printed name of the user, his account number, the card number and the like. Furthermore, the user's signature is present on a special signature field. When the card is handed out, the user is usually requested to put his signature in the special signature field.
In order to avoid forgery and falsification, the identity cards are produced and designed in such a way as to rule out imitation and/or fraudulent manipulation of the card.
The safety measures include the card structure itself. For example, a multilayer card structure made of plastic, in which the data are located in the interior of the card between layers welded together using heat and pressure, prevents direct access to the data and thus their falsification.
A further safety feature is a so-called security print, usually a guilloche print but possibly also a logo, a microprint of sequences of letters and numbers and the like. Due to their complicated design, such security prints serve in particular to prevent both total forgeries--i.e. complete reproductions--and falsification.
A frequent object of such unauthorized manipulation is the signature of the authorized user located on the card. In order to rule out falsification, i.e. manipulation, of these signatures, particularly the signature field must thus be equipped with special safety features to prevent the signature of the authorized card user from being removed and replaced by a manipulator's signature. Since the signature is generally written on the surface of the finished card, the signature field must firstly take up the ink permanently, and secondly be designed in such a way that any attempts at erasure will lead to a change in the signature field that can be checked by anyone and is preferably conspicuous.
Various methods and measures have been proposed for protecting signature stripes from forgery, i.e. reproduction and/or manipulation.
German patent no. 27 56 692 describes an identity card in which a signature stripe made of paper or plastic and provided with steel intaglio printing is laminated onto the card body. Since the signature stripe is very difficult to imitate due to the special and complicated steel intaglio print, there is a relatively low risk of the proper stripe being replaced by a forged stripe.
German laid open print no. 16 46 225 shows an identity card having a glued-on signature stripe equipped with a security pattern that is destroyed by any attempt to remove the old signature, and thereby exposes a warning print (void). However, one could fundamentally replace the destroyed signature stripe by a reproduction.
It has also been proposed to make a signature stripe printed onto the card body unforgeable by using special inks, e.g. fluorescent inks (German patent no. 28 01 015, European laid open print no. 176 403). An otherwise valid identity card of this type could also be provided with a forged signature stripe. German patent no. 34 22 908 describes an identity card in which a hologram additionally provided in the signature field is to protect the signature stripe from forgery that is provided on the card body by the hot embossing technique. However, the production of such cards using the hot embossing technique is elaborate, and the hologram can be replaced by a deceptively similar metallically reflecting image (simulacrum counterfeit).
Apart from the above-mentioned attempts to make the signature stripe unforgeable, there are also proposals according to which the signature is invisible when regarded in daylight or artificial light from usual light sources and can only be made visible using special light sources, e.g. using a UV lamp. This limits the possibilities of checking so as to be unacceptable in many cases.
British laid open print no. 2 040 807 describes an identity card wherein a microcapsule layer located within the card body is discolored by application of pressure from the outside, e.g. using a hard pen, so that the signature can be provided subsequently in the interior of the card. However, the constant use of this card and the unavoidable mechanical stress thereby destroys more and more microcapsules so that the card shows an undesirable coloration.
U.S. Pat. No. 2,545,804 describes an identity card having a paper inlay and a plastic coating on both sides, one plastic layer having a window through which the free place in the paper inlay can be written on. However no precautions were taken for protecting the signature from forgery.
The above-described known identity cards have the common feature that the signature must be made personally. Along with identity cards of this kind, there are also those in which the signature is applied by electrophotographic means or by a laser. German patent no. 29 33 436 shows an identity card in which not only the user-related information (card number, account number and the like) but also the signature are applied electrophotographically to a security paper inlay which is then laminated with plastic films on each side. German patent no. 29 07 004 describes an identity card in which all user-related information, including the signature, is burned into the paper inlay through a transparent cover film.
However, the invention is based on the problem of providing an identity card which is easy to produce and allows for the signature to be written on the signature field, after completion of the card, visibly and in a form that subsequently cannot be changed, in particular replaced. Another objective is to state a method for producing such an identity card.
This problem is solved by the invention stated in claim 1 and claim 6. Advantageous developments are stated in the subclaims.
In the inventive identity card, the security print normally provided on the card body for security purposes extends across the signature field applied, for example, by the screen printing technique. The predetermined pattern of the security print is continuous on the boundary between the signature field and the surroundings of the signature field. It is virtually impossible to detach the material of the signature field and replace the detached field by another field, since the security print--if it is imitable at all--can certainly not be adapted continuously to the print in the surrounding area of the signature field. The color coordination of the signature print on the signature field and surroundings also rules out forgery. The signature field, which hitherto had a clearly independent appearance, can be readily included in the overall appearance of the inventive identity card.
In particular, the production of the signature field can be readily included in the production process for the card body. Both the security print and the signature field can be produced e.g. by the screen printing technique. In order to protect the card after the security print has been applied, one preferably provides a transparent protective layer on the security print, the protective layer leaving a window through which the signature can be subsequently provided on the signature field.
A further measure for increasing the protection from forgery is that the security print is aperiodic from card to card. Security prints, e.g. guilloche prints, usually have periodic patterns and according to the invention the card length, for example, is not an integral multiple of the pattern periodicity.
In the inventive method, the signature field is first applied and only then the security print, in such a way that the print at least partly overlaps the signature field. The special advantages of the method are apparent when the signature field is produced e.g. by screen printing and then the security print applied continuously across the signature field from the surroundings existing in the form of a plastic surface. Both method steps are customary printing methods which can be carried out with relatively little effort. In order to obtain a very fine security print in particular in the signature field and in the area of the boundary between the signature field and the surroundings, one can perform an intermediate lamination between the screen printing operation and the security printing operation. This intermediate lamination smooths the surface of the card body provided with the signature field, so that the security print can be applied to a homogeneous, flush surface.
To protect the card one preferably provides a transparent cover film, leaving out the area of the signature field. Instead of a cover film, which has a thickness of about 80 .mu.m, one can also apply a substantially thinner layer of varnish consisting of artificial resin, e.g. two-component resin, UV-hardenable resin or the like, again leaving out the signature field. Such a layer of varnish has about the same height as the screen printing of the signature field (about 10 .mu.m). If the card body is varnished with artificial resin the window can be formed by printing technology. After varnishing the card can be completed by another lamination to make the card surface completely smooth.